Preheat oven to 375°F. Line muffin tin with muffin cups.
Place raisins in a small bowl and cover with hot water. Set aside.
Whisk the whole-wheat flour, all-purpose flour, baking powder, salt and cinnamon in a large bowl. Stir in the bran.
Whisk egg, milk, apple butter, Splenda brown sugar, oil, and molasses in a large bowl until blended. Make a well in the dry ingredients and pour in the wet ingredients.
Drain the raisins; add them and the diced apple to the bowl. Stir until just combined. Scoop the batter into the prepared pan (the cups will be very full).
Bake the muffins until the tops spring back when touched lightly, 18 to 22 minutes.